Manufacture of lubricating oils

ABSTRACT

Lubricating oils of improved viscosity index are prepared from residue-containing oils by a procedure comprising solvent extraction, hydrocracking, deasphalting and dewaxing.

United States Patent [1 1 Mead et al.

[ 51 Dec. 30, 1975 [54] MANUFACTURE OF LUBRICAT ING OILS [75] Inventors: Theodore C. Mead, Port Arthur;

William B. Ashton, Nederland; John P. Shillinglaw, Jr., Houston, all of Tex.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: June 26, 1974 [21] Appl. No.: 483,255

[52] U.S. Cl. 208/87; 208/18; 208/95 [51] Int. Cl. [58] Field of Search [5 6] References Cited UNITED STATES PATENTS 2,975,121 3/1961 Whaley 208/251 R 3,652,448 3/1972 Cummins 208/87 3,776,839 12/1973 Ladeur 208/95 3,779,896 12/1973 Woodle 208/18 Primary Examiner-Herbert Levine Attorney, Agent, or Firm-Th0mas H. Whaley; Carl G. Ries phalting and 'devyaxing.

10 Claims, N0 Drawings MANUFACTURE OF LUBRICATING OILS This invention relates to the manufacture of lubricating oils. More particularly, it is concerned with a processing sequence in which good yields of high viscosity index lubricating oils are obtained.

In the refining of crude petroleum oils it is customary to fractionally distill the crude oil at atmospheric pressure to recover gasoline, naphtha, kerosene and atmospheric gas oils as overhead, leaving as still bottoms an atmospheric residuum. Distillation is then continued at reduced pressure and there is obtained overhead vacuum gas oils and light lubricating oil distillates, leaving as still bottoms a vacuum residuum. Frequently the vacuum residuum is burned as a residual fuel, but in view of the growing shortage of crude oils and the' greater demand for lubricating oils, it has become customary to conyert the vacuum residuum, by further processing, to lubricating oils. Conventionally, the processing comprises subjecting the residuum to a deasphalting treatment by contact with a low molecular weight normal paraffin such as propane or butane. To increase the viscosity index of the deasphalted residuum it is catalytically hydrocracked and the portion of the hydrocracked product boiling in the lubricating oil range is subjected to solvent refining which comprises contacting the oil with a solvent having an affinity for aromatic hydrocarbons such as furfural, phenol, N- methyl-2-pyrrolidone and the like for the removal of aromatics. To reduce its pour point, the oil is then subjected to a dewaxing treatment.

In each of the processing steps listed above, there is a considerable loss in yield so that the final yield of refined lubricating oil actually obtained may amount to only about 30 volume percent based on theoriginal charge of vacuum residuum. Another problem is that most refineries are hampered by the small capacity of the deasphalting unit which means that ordinarily to increase the production of lubricating oils from a vacuum residuum, it would be necessary to construct additional facilities to increase the deasphalting capacity of the refinery.

It is therefore an object of this invention to produce lubricating oils from heavy stocks such as vacuum residua. Another object of this invention is to increase the capacity of refineries for the production of lubricating oil from vacuum residua without building additional deasphalting facilities.

According to our invention a heavy residue-containing petroleum oil is converted to a lubricating oil of high viscosity index by a procedure which comprises solvent refining the residue-containing oil by contact.- ing same with a liquid having an affinity for aromatics to extract aromatic compounds from the oil, catalytically hydrocracking the resulting raffinate, recovering from the hydrocracked product a fraction boiling in the lubricating oil range, subjecting said fraction to a delayed deasphalting treatment by contacting same with a low molecular weight paraffin such as propane or butane and then subjecting the deasphalted oil to a dewaxing treatment.

The charge stocks used in the process of our invention are those containing materials boiling within the lube oil range and also containing at least 5 weight percent Conradson carbon residue. To obtain a highviscosity index product the viscosity index of the charge stock preferably should be at least about 70, but

the process is not limited to such charge stocks. Charge stocks having'viscosity indices of 50 and lower may be used successfully to produce high-viscosity index products using more severe processing conditions. Suitable charge stocks include atmospheric and vacuum residua obtained from West Texas, Mid-Continent, Arabian, or other paraffin-base crude oils, and in some cases, whole crudes such as San Ardo crude.

In the solvent refining step the residuecontaining charge stock is subjected to liquid-liquid contact with a selective solvent which preferentially dissolves the aromatic constituents of the charge. It is a characteristic of the solvent employed that it is partially miscible with the charge undergoing treatment so that during the solvent refining step, two phases are formed: a raffinate phase containing substantially only a solvent refined material having a reduced amount of aromatics as compared to the charge stock and an extract phase containing substantially more aromatics than the charge stock. The solvent refining step may be carried out batchwise or may be carried out continuously in a suitable contacting apparatus such as a packed or plate tower or a rotating disc contactor, either concurrently or countercurrently.

The contacting is carried out at a temperature above about 50F. but below the boiling point of the solvent, preferably about 50F. below the boiling point. The temperature should also be below the temperature of complete miscibility of the charge in the solvent. Ordinarily an extraction temperature between 50 and 250F. is employed. A solvent dosage within the range of about 50500% may be used, a range between about 100 and 200 volume percent and a temperature between 150 and 200F. being preferred for the solvent refining of paraffin base charge stocks. When the charge is of the naphthenic type, temperatures of from 50 to 200F., preferably from 200F., may be used with dosages of from 50 to 300 volume percent, preferably from 75 to 200 volume percent. Furfural and N- methyl-Z-pyrrolidone are the preferred agents for the solvent refining. N-methyl-Z-pyrrolidone is particularly preferred because of its greater thermal stability and its superior solvent power.

After residual solvent has been removed by stripping, the raft'mate is then subjected to catalytic hydrocracking at a temperature between about 650 and 850F., a pressure between about 1000 and 3000 psig, a space velocity from about 0.1 to 5.0 volumes of oil per volume of catalyst per hour in the presence of hydrogen introduced at a rate between about 1000 and 10,000 standard cubic feet per barrel of charge. Preferably the temperature is maintained within the range of 700-850F., the pressure between 1300 and 3000 psig, the space velocity between 0.15 and 1.5 v/v/hr and the hydrogen rate between 3000 and 10,000 SCFB.

For the hydrocracking, hydrogen from any suitable source such as electrolytic hydrogen, catalytic reformer byproduct hydrogen or hydrogen obtained from the partial combustion of hydrocarbonaceous materials followed by shift conversion and CO removal may be used. The hydrogen should have a purity of at least 50%, with hydrogen purities of from 75 to volume percent being preferred.

Suitable hydrocracking catalysts for use in the process of our invention comprise as hydrogenating components metals or compounds of metals of Group V1 and Group VIII of the Periodic Table. Examples of such components are chromium, molybdenum, tung- 3 sten, iron, cobalt, and nickel, and mixtures thereof. Ordinarily these metals are present as the oxide or sulfide'These hydrogenating components may be supported on, a base comprising an amorphous refractory inorganic oxide material such as alumina, silica, magnesia, zirconia, titania and the like, and mixtures thereof, optionally in conjunction with'a crystalline alumino silicate of reduced alkali metal content and having uniformpore openings of from 6 to 15A such as low sodium zeolite Y. The catalyst may be used in the form of a slurry, a fluidized bed or a fixed bed. When used in the form of a fixed bed, which is preferred, the

reactant vflow may be either upward or downward, or the flow of hydrogen may be upward contercurrent to the downward flow of the oil. Particularly suitable catalysts are those containing from 1 to 10 weight percent Zweight percent, preferably between about 2 and 30 weight percent. Ordinarily the catalyst is charged to the F ctor as the oxide, but may be sulfided in situ prior to the, hydrocracking or may become partially .sulfided during the course of the reaction when sulfur is present in the hydrocarbon oil.

Hydrogen and low molecular weight hydrocarbons are flashed from the effluent from the hdyrocracking zone and the remainder is then distilled to remove components, boiling below the lubricating oil range, usually those materials boiling up to about 650-675F. Deasphalting of the remaining lubricating oil is effected by. contact with a low molecular weight paraffin deasphalting agent such as propane, normal butane, isobu- .tane or pentane at a temperature in the range of l250? F., a dosage-of from 400 to 1000 volume percent anda pressure of between about 200 and 600 psig. Preferred conditions are temperature of l50225F., dosages of 400-800 volume percent, and pressures betweenabout 400 and 500 psig. Advantageously, the temperature does not exceed the critical temperature of the solvent and the pressure is held somewhat above the autogenous pressure to prevent vaporization. Asphalt is removed from the contacting zone separately from the deasphalted oil and deasphalting agent.

Thedeasphalting agent is then removed by evaporation and stripping and the solvent extracted, hydrocracked, deasphalted oil is subjected to dewaxing. In one embodiment of our invention the deasphalted oil is passed thorugh a bed of pelleted catalyst comprising a hydrogenating component such as is used in the hydrocracking catalyst in substantially the same amounts supported on a decationized mordenite which has been composited with an amorphous inorganic refractory oxide such as silica or alumina. 1n the preparation of the support, synthetic mordenite is treated with a dilute acid such as 6N HCl to the extent that a portion of .the

alumina is leached out of the mordenite to produce a mordenite having a silicazalumina mole ratio of at least 20 and is then mixed with the amorphous oxide. The catalytic dewaxing may be carried out at a temperature of at least 450F., a pressure of at least psig, and a space velocity of from 0.2 to 5.0 v/v/hr. in the presence of hydrogen introduced at a rate between about 1000 and 10,000 SCFB. Preferred conditions are a temperature of 490-850F., a pressure between 100 and 1500 psig, a space velocity between 0.2 and 1.0 v/v/hr. with a hydrogen rate between 3000 and 8000 SCFB.

In another embodiment of our invention the dewaxing is effected by contacting the solvent-extracted, hydrocracked, deasphalted oil with a dewaxing agent such as a mixture of dichloromethane and dichloroethane or a mixture of a ketone such as acetone, methyl ethyl ketone or normal butyl ketone and an aromatic hydrocarbon such as benzene or toluene in a ratio of from 3 to 5 parts by volume of solvent per volume of oil and cooling the oildewaxing agent mixture to a temperature of from about 0l0F. below the desired pour point of the dewaxed oil. The waxy components may then be removed by filtering or centrifuging. If desired, the filtrate or supernatant liquid may be subjected to an additional wash with solvent prior to stripping for removal of the residual solvent. The preferred solvent is a mixture composed of 60 volume percent methyl ethyl ketone and 40 volume percenttoluene used at a solventzoil ratio of 4:1 followed by a wash using a solvent- :oil volume ratio of 3:1.

The following example is submitted for illustrative purposes only, and it should not be construed that the invention is limited thereto.

The chargein this example is a vacuum residuum having an API gravity of 17.6, a viscosity SUS at 210F. of 474, a carbon residueof 7.9 wt. a sulfur content of 0.59 wt. anda total nitrogen content of 2158 ppm. It is solvent-extracted by being contacted with N-methyl-Z-pyrrolidone at 100 volume percent dosage at a temperature of F. The raffinate from the solvent extraction is hydrocracked by being passed through a bed of pelleted catalysts having a composition of 2.2 wt. cobalt, 9.9 wt. molybdenum, 3.9 wt. silica, and the balance alumina at a temperature of 81551 a pressure of 1600 psig, a space velocity of 1.0 v/v/hr. at a hydrogen rate of 5000 SCFB. A lubricating oil fraction having an initial boiling point of 650F. is recovered from the hydrocracking zone effluent and is subjected to deasphalting with propane at 400 p.s.i. and at an initial dosage of 800 vol. with a wash of 200 vol. at a temperature of 180F.

The solvent-extracted, hydrocrackeddeasphalted oil is then dewaxed by being mixed with a dewaxing solvent composed of 60 volume methyl ethyl ketone and 40 volume toluene. The solvent is mixed with the oil in a volume ratio of 4 parts of solvent per part of oil and the mixture cooled to a temperature of -5F. The precipitated wax is filtered from the mixture which is then given a wash with solvent in a volume ratio of 3 parts of solvent per part of oil.

In the following table, the oil properties after each processing step are listed:

-continued SOL- HYDRO- DE- SOLVENT VENT CHAR- REF. CRACK AS- DEWAX GE PHALT Overall Yield. Wt.% 68.0 52.9 47.8 42.1 Gravity, AP1 17.6 23.4 28.6 31.2 28.4 Viscosity, SUS at 100F. 427 386 450 210F. 474 213 62.8 60.1 62.3 Viscosity lndex 83 1 l3 1 105 Pour. F. 120+ 120+ 40 40 5 Refractive Index 1.5165 1.4884 1.4730 1.4623

at 70C. Carbon Residuc,Wt.% 7.9 2.86 1.30 0.1 0.1 Sulfur, Wt. 0.59 0.36 0.045 0.02 0.02 Total N, ppm 2158 857 303 45 50 Color. Lovi, 6" 45 Since most refineries have limited deasphalting capacity but have ample solvent refining capacity, by following the procedure exemplified above, it is now possible in a refinery having a deasphalting capacity of 5000 barrels per day to produce 3,978 bpd of refined lube oil whereas by following the conventional procedure where deasphalting is the first step, the refinery would have a maximum capacity of about 1870* barrels of finished oil per day. Another economic advantage is that a large proportion of the oil is subjected to the less expensive solvent refining and,a smaller proportion of the oil is subjected to the more expensive deasphalting.

* assumes only 80.4% deasphalting yield for raw residuum Obviously, various modifications of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be made as are indicated in the appended claims.

We claim:

1. A process for the production of a lubricating oil which comprises contacting a residue-containing oil with a solvent having an affinityfor aromatics to extract aromatic compounds from the oil, catalytically hydrocracking resulting raffinate, recovering from the hydrocracked product a fraction boiling in the lubricating oil range, subjecting said fraction to deasphalting treatment by contacting same with a low molecular weight paraffin and subjecting the deasphalted oil to a dewaxing treatment.

2. The process of claim 1 in which the residue-containing oil is a vacuum residuum.

3. The process of claim 1 in which the residue-containing oil is an atmospheric residuum.

4. The process of claim 1 in which the viscosity index of the residue-containing oil is less than 70.

5. The process of claim 1 in which the fraction boiling in the lubricating oil range has an initial boiling point between 650 and 675F.

6. The process of claim 1 in which the solvent having an affinity for aromatics is N-methyl-Z-pyrrolidone.

7. The process of claim 1 in which the low molecular weight paraffiri is propane.

8. The process of claim 1 in which the dewaxing is effected by contacting the deasphalted oil with a catalyst comprising a hydrogenating component on a sup port comprising acid'leached mordenite having a silicaalumina mol ratio of at least 20:1 under dewaxing conditions. I

9. The process of claim 1 in which the dewaxing is effected by meansof a solvent.

10. The process of claim 9 in which the solvent is a mixture of methyl ethyl ketone and toluene. 

1. A PROCESS FOR THE PRODUCTION OF A LUBRICATING OIL WHICH COMPRISES CONTACTING A RESIDUE-CONTAINING OIL WITH A SOLVENT HAVING AN AFFINITY FOR AROMATICS TO EXTRACT AROMATIC COMPOUNDS FROM THE OIL, CATALYTICALLY HYDROCRACKING RESULTING RAFFINATE, RECOVERING FROM THE HYDROCRACKED PRPDUCT A FRACTION BOILING IN THE LUBRICATING OIL RANGE, SUBJECTING SAID FRACTION TO DEASPHALTING TREATMENT BY CONTACTING SAME WITH A LOW MOLECULAR WEIGHT PARRAFIN AND SUBJECTING THE DEASPHALTED OIL TO A DEWAXING TREATMENT.
 2. The process of claim 1 in which the residue-containing oil is a vacuum residuum.
 3. The process of claim 1 in which the residue-containing oil is an atmospheric residuum.
 4. The process of claim 1 in which the viscosity index of the residue-containing oil is less than
 70. 5. The process of claim 1 in which the fraction boiling in the lubricating oil range has an initial boiling point between 650* and 675*F.
 6. The process of claim 1 in which the solvent having an affinity for aromatics is N-methyl-2-pyrrolidone.
 7. The process of claim 1 in which the low molecular weight paraffin is propane.
 8. The process of claim 1 in which the dewaxing is effected by contacting the deasphalted oil with a catalyst comprising a hydrogenating component on a support comprising acid-leached mordenite having a silica-alumina mol ratio of at least 20:1 under dewaxing conditions.
 9. The process of claim 1 in which the dewaxing is effected by means of a solvent.
 10. The process of claim 9 in which the solvent is a mixture of methyl ethyl ketone and toluene. 